The invention relates to a heat cycle machine which operates according to the Stirling cycle and can be used as a multi-valent, that is to say using various energy sources (sunlight, combustion of available materials), stand-alone power supply for households in order to generate electricity and heat, particularly suited as isolated application.
State-of-the-art heat cycle machines are known to be based on the Stirling engine, which has been developed and optimized over more than a century using increasingly modern materials. These machines together are based on the principle of circular process work as calculated in advance by Gustav Schmidt in the 1870s, taking into account dead volumes, different loading pressures, various temperature differences, running speeds and much more.
The well-known design of Stirling engines, in which displacement and working pistons are coupled mechanically, e.g. by means of a linkage, was largely retained in the course of optimization. The Ringbom engine and the latest low-temperature Stirling engines are an exception.
The conversion of thermal energy into mechanical work using pistons necessarily entails a cyclic acceleration and deceleration of the piston mass, as a result of which the efficiency is reduced. DE 10 2008 048 633 B4 and DE 10 2008 048 639 B4 describe a piston-less system, which operates according to the Stirling principle, wherein two chambers, being alternately cooled and heated, are each connected via a fluid line to a turbine driven by the working gas flowing back and forth between the two chambers.
EP 2 037 113 A2 furthermore discloses a heat engine having two displacement pistons in two chambers, each having different temperature-controlled sides, which displacement pistons convey a working gas to a piston of a working machine. Both chambers arranged next to one another have a double-walled construction with cooling or heating media circulating therein. The vertically moved displacement pistons are coupled, for example by means of a control chain.
A further problem of, in particular, heat cycle machines operating under boost pressure is their tightness, since—due to the design principle of the machines—the working gas (mostly helium) constantly leaks and therefore has to be refilled accordingly. The torque which is eventually to be converted into electrical or mechanical power, is taken off the heat cycle machine by means of a generator, pump or the like mounted on the working shaft; that is to say that the constantly rotating shaft must be sealed in a helium-tight manner at the position, at which it is led out of the machine housing. The only exception to this principle is the use of a linear generator for power generation, which is integrated directly into the wall of a working cylinder, wherein in this case, however, moving pistons are used again.
In order to gain a considerable amount of mechanical energy, a high temperature gradient, high charging pressures and the resulting high demands on the materials, which themselves cannot be lubricated, are required. The costs are correspondingly high for a machine that is usually permanently mounted on a dedicated energy source in order to be optimized.